Fire extinguisher cylinders generally include Chlorofluorocarbons (CFC's), Hydrochlorofluorocarbons (HCFC's) and Hydrofluorocarbons (HFC's) in the cylinder as fire-fighting agents.
When it is necessary to empty such a cylinder for servicing, repair or pressure testing, the valve on the cylinder is opened and the contents thereof allowed to escape under their own vapour pressure into the atmosphere. This has the disadvantage of being highly wasteful and furthermore such release of halogenated hydrocarbons is highly damaging to the ozone layer and hence extremely undesirable from an environmental point of view.
The present invention is particularly concerned with fire extinguisher cylinders containing halogenated hydrocarbon vapours including Halon 1211, Halon 1301, (CF.sub.3 BR) Halon 2402, Refrigerant R13B1 and Refrigerant R22, for example, either on their own or superpressurized with nitrogen.
The term "halon" will be used hereafter to mean any of the above halogenated hydrocarbons, by way of example to illustrate the operation of the various aspects of the invention. The term "fluid" will be taken to include liquid, vapour and gas.